FXUS65 KGJT 102236
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
336 PM MST THU DEC 10 2009
...SNOW RETURNS THIS WEEKEND...
.SHORT TERM...TONIGHT THROUGH SATURDAY...
ANOTHER VERY COLD NIGHT IN STORE TONIGHT...ESPECIALLY FOR THE VALLEYS
WHERE STABLE CONDITIONS HAVE LIMITED THE AMOUNT OF MIXING TODAY. LOWS
TONIGHT WILL BE COMPARABLE TO LAST NIGHT IN MANY LOCATIONS. A VERY
WEAK UPPER DISTURBANCE WILL DRAG SOME CLOUDS ACROSS THE SOUTH
TONIGHT. PATCHY FOG AGAIN POSSIBLE. GRADUAL WARMING ALOFT WILL SLOWLY
MODERATE TEMPERATURES AND THE HIGHER ELEVATIONS...BUT REINFORCE
INVERSIONS IN THE VALLEYS TONIGHT AND FRI.
ATTENTION FOCUSES ON THE WEEKEND NOW AS A WESTERLY PACIFIC JET PUSHES
INLAND ACROSS CA AND INTO THE SRN GREAT BASIN IN THE NEXT 48 HRS...
BRINGING WITH IT A SERIES OF SHORTWAVE DISTURBANCES AND INCREASING
MOISTURE.
CLOUDS ON THE INCREASE FRI AHEAD OF THE FIRST WAVE CURRENTLY EXPECTED
TO CROSS OVERHEAD FRI NIGHT. THIS DISTURBANCE WEAKENS BUT LOOKS TO
HAVE SUFFICIENT MOISTURE AND ISENTROPIC LIFT FOR 1-3 INCHES OF SNOW
OVER MOST MTNS...FAVORING THE WEST AND SOUTHWEST SLOPES. ANTICIPATE A
BIT OF A DOWNTURN IN PRECIP ON SATURDAY BEHIND THIS INITIAL
DISTURBANCE...ALTHOUGH LIGHT SNOW COULD PERSIST ON/OFF FOR MUCH OF
THE TIME AT SOME CENTRAL AND SRN MTN LOCATION IN THE W-SW FLOW.
POTENTIAL INSTABILITY INCREASES SOMEWHAT ALOFT SAT AFTERNOON...WHICH
COULD ACCENTUATE ANY LIFT FROM UNRESOLVED DISTURBANCES OR WEAK
ISENTROPIC/OROGRAPHIC LIFT AT LOWER LEVELS. SNOW AMOUNTS SAT ARE ALSO
EXPECTED TO BE LIGHT...WITH THE BULK OF THE SNOW LATER IN THE WEEKEND
AS DISCUSSED BELOW IN THE LONG TERM SECTION. LATER SHIFTS CAN
EVALUATE FURTHER AS MODELS OFTEN STRUGGLE WITH TIMING WAVES IN FAST
ZONAL /WESTERLY/ FLOW.
.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
THE MOIST AND ENERGETIC WESTERLY FLOW WILL INCREASE SATURDAY NIGHT AS
THE NEXT WAVE IN THE SERIES APPROACHES THE FORECAST AREA. MOISTURE
WILL DEEPEN SAT NIGHT AND SUN WITH MODELS STILL SHOWING OVER 4 G/KG
OVER THE FOUR CORNERS BY EARLY SUNDAY. TIMING STILL UNCERTAIN WITH
THE STRONGEST SHORTWAVE...NOW TIMED FOR SUNDAY NIGHT. HOWEVER MODELS
INDICATE THE MOISTURE PLUME...AND A COUPLE HARD TO RESOLVE IMPULSES
OUT AHEAD OF THIS STRONGER WAVE. THEREFORE SAT NIGHT THROUGH SUN
NIGHT WILL SEE THE BEST PRECIPITATION...WITH THE NEED FOR HILITES
ANTICIPATED. SO HAVE UPPED POPS OVER THE MOUNTAINS TO CATEGORICAL FOR
THESE PERIODS...WITH SNOW IN SOME VALLEYS BECOMING LIKELY ON SUNDAY.
INITIALLY THE SOUTHERN MOUNTAINS WILL BE FAVORED...WITH HEAVY SNOW
DEVELOPING OVER ALL MOUNTAIN AREAS BY EARLY SUNDAY. THEN THE BY LATE
SUNDAY NIGHT THE FOCUS SHIFTS TO THE NORTHERN MOUNTAINS.
MONDAY WILL SEE A DOWNTURN...BUT ENOUGH MOISTURE/INSTABILITY WILL
REMAIN IN THE LOWER LEVELS FOR A CONTINUATION OF OROGRAPHIC SNOW OVER
THE MOUNTAINS...ESPECIALLY ALONG THE DIVIDE. SOME ACTIVITY WILL
LINGER OVER THE NORTHERN MOUNTAINS THROUGH MONDAY NIGHT.
RIDGING THEN DEVELOPS OVER THE WEST THROUGH THE REMAINDER OF THE
PERIOD FOR A DRIER NORTHWEST FLOW OVER OUR FORECAST AREA. INVERSIONS
WILL AGAIN SET UP IN MOST VALLEYS WITH SNOW STILL ON THE GROUND...BUT
CONDITIONS ARE NOT EXPECTED TO BE QUITE AS COLD AS THE LAST COUPLE OF
DAYS.
&&
.AVIATION...
VFR CONDITIONS EXPECTED OVER THE REGION THROUGH 18Z FRI. HOWEVER...
PATCHY FOG WILL OCCASIONAL RESTRICT CIGS AND VSBYS INTO THE MVFR/IFR
CATEGORIES...ESPECIALLY NEAR AIRPORTS BLANKETED IN SNOW COVER.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&
$$
SHORT TERM...JAD
LONG TERM....EH
AVIATION.....TGJT
